Although headgear having a retractable visor slideably mounted under a fixed brim or visor, or a releasably attachable brim or visor extension fastenable to a fixed brim or visor are well known, these structures are generally only capable of extending either the length or the width of the visor, not both the length and width. For example, U.S. Pat. No. 5,621,915 discloses a removable cap visor extension that is attachable to a visor of a cap or hat either by sliding the visor through slots in an extension unit or by clasping the extension unit onto a visor of a cap with fasteners. The removable cap visor is not retractable, but instead is either attached or not attached to the cap or hat. Accordingly, the disclosed removable cap visor does not allow continuously variable adjustment of the length and does not allow any adjustment of the width of the visor.
U.S. Pat. No. 6,202,218 discloses a hat having an extensible visor which is inserted into a slot of a fixed visor or brim to facilitate variable adjustment of the length of the visor. However, the disclosed extensible visor does not permit variable adjustment of both the length and width of the visor.
U.S. Pat. No. 5,689,830 discloses a visor for use as a brim component for a hat or cap. The brim is both retractable and extendable, and is also swivelable and rotatable around the circumference of the head of the wearer. However, the visor is only swivelable with respect to the hat, and does not allow pivoting of the extensions with respect to the fixed brim to adjust the width of the visor.
U.S. Pat. No. 5,901,371 discloses a cap with adjustable side visors disposed on opposite sides of a main fixed visor. Each side visor has a flap pivotally mounted thereto which is moveable from a first position disposed within the respective side visor to a second position extending downwardly therefrom to vary the shading desired by the user. However, the flaps do not provide a visor extension that achieves variable adjustment of both the length and width of the visor.
Other patents that disclose caps having an extensible visor that allows adjustment of the  length of the visor, but not the width of the visor, include U.S. Pat. Nos. 4,793,006; 5,075,898; 5,197,150 and 5,839,125. These patents all recognize the desirability of being able to adjust the length of a visor, whereas U.S. Pat. No. 5,901,371 recognizes the desirability of being able to adjust the length of a side visor portion to provide more shading on one or both sides of the cap. However, none of these patents acknowledge the desirability of being able to adjust both the length and width of a visor, and none of these patents suggest a suitable structure for achieving adjustment of both the length and width of a visor.
The art relating to structures having a support surface with an area that is adjustable is perhaps best exemplified by the furniture art. Heretofore, most tables, desks, and other articles of furniture having a variable area support surface generally utilized a removable leaf, or a leaf extension that is either slideably mounted, or pivotally mounted to the furniture for rotation from a vertical orientation to a horizontal orientation. These extensible structures have certain disadvantages. For example, removable leaves do not allow variable adjustment of the surface area on which items may be supported on the table or other article of furniture, and must generally be transported to and from a storage location when a larger or smaller surface area is desired. Leaves that are either pivotally or slideably connected to the article of furniture eliminate the need for storage and transportation. However, the slideably mounted leaves only allow adjustment of either the length or width of the support surface of an article of furniture, not both the length and width. Similarly, the leaves that are rotatably mounted to the support surface of an article of furniture are typically rotatable through an axis substantially within the plane of the support surface of the article of furniture from a vertical to a horizontal orientation, and therefore only allow expansion of either the length or width of the table, not both, and do not provide the option of variable adjustment of the support surface area.
Similar structures used to supplement the surface area in other environments typically suffer from the same disadvantages of furniture having conventional extensible/retractable leaves.